Workers exposed to asbestos and cigarettes have a markedly increased risk of developing lung cancer and parenchymal fibrosis. Airway metaplasia and inflammation on bronchoalveolar lavage (BAL) are considered potential early markers of these diseases. Our prior studies have shown a high incidence of both of these lesions in asbestos-exposed workers. Epidemiologic and experimental studies have shown that dietary vitamin A (retinol and B-carotene) has significant anticancer and immunomodulatory effects. However, whether intervention with vitamin A can reduce the mortality or morbidity from either disease and the mechanisms involved are unknown. Asbestos-exposed workers thus serve as an excellent population to test our hypotheses that: 1) Vitamin A intervention will reduce both bronchial metaplasia and lung inflammation, 2) The mechanism of this effect is through modulation of relevant pulmonary cytokines and 3) Local lung rather than serum retinol levels may be a key modifiable biomarker of susceptibility to lung cancer and/or asbestosis. To test these hypotheses we propose the following specific aims: 1) Determine the effect of dietary vitamin A on bronchial metaplasia and lung inflammation, 2) Investigate the possible mechanisms involved by determining the expression of relevant lung cytokines, and 3) Determing whether BAL retinoid and caroteniod levels correlate with early markers of disease and can be modified by the intervention. Identifying early markers of disease and markers of host susceptibility should greatly facilitate such occupational studies. The general approach will be a double-blind placebo controlled 6 month trial of combination B-carotene and retinol. The findings may lead to effective preventive strategies for lung cancer and asbestosis.